package unit;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * CWE-407 unit test: solr-001
 * ClusterStatus.java:303 — liveNodes.contains(node_name) (List) inside double
 * loop over shards × replicas — O(N × S × R) per CLUSTERSTATUS request.
 *
 * Slow path: List<String>.contains() — O(N) per replica.
 * Fast path: HashSet<String>.contains() — O(1) per replica.
 *
 * Compile: javac -d . ClusterStatusLiveNodesContains.java
 * Run:     java -ea unit.ClusterStatusLiveNodesContains
 */
public class ClusterStatusLiveNodesContains {

    /** Simulates a Replica record. */
    static class Replica {
        String nodeName;
        String state; // "active" or "down"
        Replica(String nodeName, String state) {
            this.nodeName = nodeName;
            this.state = state;
        }
    }

    /** Simulates a Shard record. */
    static class Shard {
        List<Replica> replicas;
        Shard(List<Replica> replicas) { this.replicas = replicas; }
    }

    /**
     * Simulates the defective crossCheckReplicaStateWithLiveNodes.
     * Returns total comparison count (liveNodes.contains() calls × avg scan length).
     */
    static long slowCrossCheck(List<String> liveNodes, List<Shard> shards) {
        long comparisons = 0;
        for (Shard shard : shards) {
            for (Replica replica : shard.replicas) {
                if (!"down".equals(replica.state)) {
                    // O(liveNodes.size()) scan
                    comparisons += liveNodes.size();
                    if (!liveNodes.contains(replica.nodeName)) {
                        replica.state = "down";
                    }
                }
            }
        }
        return comparisons;
    }

    /**
     * Simulates the fixed crossCheckReplicaStateWithLiveNodes using HashSet.
     * Returns total hash operations (O(1) each).
     */
    static long fastCrossCheck(List<String> liveNodes, List<Shard> shards) {
        Set<String> liveNodeSet = new HashSet<>(liveNodes);  // O(N) once
        long operations = 0;
        for (Shard shard : shards) {
            for (Replica replica : shard.replicas) {
                if (!"down".equals(replica.state)) {
                    operations++;  // O(1) hash lookup
                    if (!liveNodeSet.contains(replica.nodeName)) {
                        replica.state = "down";
                    }
                }
            }
        }
        return operations;
    }

    /** Build a test cluster: N live nodes, S shards, R replicas each. */
    static List<Shard> buildCluster(int S, int R, int N) {
        List<Shard> shards = new ArrayList<>();
        for (int s = 0; s < S; s++) {
            List<Replica> replicas = new ArrayList<>();
            for (int r = 0; r < R; r++) {
                // Distribute replicas across nodes; node (s*R+r) % N
                String nodeName = "node" + ((s * R + r) % N);
                replicas.add(new Replica(nodeName, "active"));
            }
            shards.add(new Shard(replicas));
        }
        return shards;
    }

    static List<String> buildLiveNodes(int N) {
        List<String> nodes = new ArrayList<>();
        for (int i = 0; i < N; i++) nodes.add("node" + i);
        return nodes;
    }

    public static void main(String[] args) {
        int passed = 0;
        int total = 0;

        // Test 1: correctness — replicas on dead nodes get marked DOWN
        {
            total++;
            List<String> liveNodes = new ArrayList<>();
            liveNodes.add("node0");
            liveNodes.add("node1");
            // node2 is dead

            List<Shard> shards = new ArrayList<>();
            List<Replica> r1 = new ArrayList<>();
            r1.add(new Replica("node0", "active"));
            r1.add(new Replica("node2", "active")); // should go DOWN
            r1.add(new Replica("node1", "active"));
            shards.add(new Shard(r1));

            slowCrossCheck(liveNodes, shards);

            assert "active".equals(shards.get(0).replicas.get(0).state) : "node0 should stay active";
            assert "down".equals(shards.get(0).replicas.get(1).state) : "node2 replica should be DOWN";
            assert "active".equals(shards.get(0).replicas.get(2).state) : "node1 should stay active";
            System.out.println("Test 1 (correctness): node2 replica correctly marked DOWN");
            passed++;
        }

        // Test 2: fast path correctness
        {
            total++;
            List<String> liveNodes = new ArrayList<>();
            liveNodes.add("node0");
            liveNodes.add("node1");

            List<Shard> shards = new ArrayList<>();
            List<Replica> r1 = new ArrayList<>();
            r1.add(new Replica("node0", "active"));
            r1.add(new Replica("node99", "active")); // dead
            shards.add(new Shard(r1));

            fastCrossCheck(liveNodes, shards);

            assert "active".equals(shards.get(0).replicas.get(0).state);
            assert "down".equals(shards.get(0).replicas.get(1).state) : "node99 should be DOWN";
            System.out.println("Test 2 (fast correctness): node99 replica correctly marked DOWN");
            passed++;
        }

        // Test 3: cost comparison — medium cluster
        {
            total++;
            int N = 50;  // live nodes
            int S = 100; // shards
            int R = 3;   // replicas/shard

            List<String> liveNodes = buildLiveNodes(N);
            List<Shard> slowShards = buildCluster(S, R, N);
            List<Shard> fastShards = buildCluster(S, R, N);

            long slowCost = slowCrossCheck(liveNodes, slowShards);
            long fastCost = fastCrossCheck(liveNodes, fastShards);

            assert slowCost > fastCost * 5 :
                String.format("Expected slow >> fast: slow=%d fast=%d", slowCost, fastCost);
            System.out.printf("Test 3 (N=%d S=%d R=%d): slow=%d, fast=%d, ratio=%.1fx%n",
                N, S, R, slowCost, fastCost, (double) slowCost / fastCost);
            passed++;
        }

        // Test 4: production-scale cluster
        {
            total++;
            int N = 100; // live nodes
            int S = 500; // shards
            int R = 3;   // replicas/shard

            List<String> liveNodes = buildLiveNodes(N);
            List<Shard> slowShards = buildCluster(S, R, N);
            List<Shard> fastShards = buildCluster(S, R, N);

            long slowCost = slowCrossCheck(liveNodes, slowShards);
            long fastCost = fastCrossCheck(liveNodes, fastShards);

            double ratio = (double) slowCost / fastCost;
            assert ratio > 20.0 :
                String.format("Expected >20x speedup at N=%d S=%d R=%d, got %.1fx",
                    N, S, R, ratio);
            System.out.printf("Test 4 (N=%d S=%d R=%d): slow=%d, fast=%d, speedup=%.1fx%n",
                N, S, R, slowCost, fastCost, ratio);
            passed++;
        }

        System.out.printf("%n%d/%d PASS%n", passed, total);
    }
}